ISSN:1124-318X    

DOI:10.1002/ett.4460020602

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1991

数据来源: WILEY

摘要:

AbstractThis paper presents the algorithm design of the SIR‐C ground data processor, with emphasis on the unique elements involved in the production of registered multi‐frequency polari‐metric data products. A quick‐look processing algorithm used for generation of low‐resolution browse image products and estimation of echo signal parameters is also presented. Specifically, we will discuss the following: 1) Azimuth reference function generation to produce registered polarimetric imagery; 2) Geometric rectification to accommodate cross‐track and along‐track Doppler drifts; 3) Multi‐look filtering designed to generate output imagery with a uniform resolution; and 4): Efficient coding to compress the polarimetric image data f

ISSN:1124-318X    

DOI:10.1002/ett.4460020603

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1991

数据来源: WILEY

摘要:

AbstractA novel, subaperture approach for high quality SAR processing has been developed at DLR. This approach is based on dividing the received SAR signal (range or azimuth direction) into small subapertures, allowing a quadratic phase variation of up to_ 115° within one subaperture. With a simple linear correction of the phase variation, the correlation process in each subaperture is reduced to an up/down frequency conversion followed by two moving average operations. By adding all the subapertures coherently, a high resolution impulse response function is obtained, which leads to the same image quality as with the conventional matched filter method. Due to the reduced amount of computation and the subaperture structure, this new approach is especially suitable for real‐time SAR processing while providing flexibility to multi‐look processing and auto‐focus. The concept of a high resolution real‐time SAR processor for the DLR's airborne E‐SAR system is discussed and a simulation result for evaluating the performance of the proposed algorith

ISSN:1124-318X    

DOI:10.1002/ett.4460020604

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1991

数据来源: WILEY

摘要:

AbstractAs opposed to Fourier and associated integral methods for SAR processing, the paper discusses a method, based on the numerical unfolding of a differential equation along the synthetic aperture path. The method is a particular case of a general approach, which also may be applied to other synthetic aperture techniques, such as ISAR and btstatic imaging. The integration process may be termedcumulative, since a low resolution image available at a certain time along the synthetic aperture, together with the data registered at this moment of time, form the basis for constructing an image of successively improved resolution. The approach seems suitable for real time imaging, motion compensation, adaptive radar, and whenever continuous control over the imaging process is required. The paper considers application of the method to the extreme situation of ultra wide band, low frequency SAR. It is not as yet known how the method compares to the more conventional correlation methods, in the case of narrow band microwave SAR. The method is demonstrated by several numerical tests.

ISSN:1124-318X    

DOI:10.1002/ett.4460020605

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1991

数据来源: WILEY

摘要:

AbstractIn SAR digital data processing, using the range‐Doppler approach, the main computational load occurs in the range and azimuth compressions, for which one‐dimensional circular convolutions in the Fourier domain are used. In the paper it is shown how the intrinsic degrees of parallelism of the process can be efficiently exploited to design a flexible parallel/pipeline multiprocessor architecture, based on advanced components with interconnection capabilities and capable to perform up to the real‐time SAR data focusing. In the proposed architecture, an efficient line compression can be achieved by means of pipelined processors for the range and the azimuth compressions and many of these structures, each performing the compression of a line or its section, can be used to sustain the computational load and the data rate requirements. In the paper, we also show how the data communication between the range and the azimuth processors can be solved when a maximum of eight of these line compressors are used.The performance evaluation of the proposed architecture is made referring to real spaceborne SAR se

ISSN:1124-318X    

DOI:10.1002/ett.4460020606

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1991

数据来源: WILEY

摘要:

AbstractThe problem of precision processing of SAR data in real time is here discussed, considering both a new performance evaluation model for structured algorithms and effective computational schemes of the SAR data compression process, in order to assess conditions of effectivereal timeprocessing possibilities in this performance demanding application. Our analysis leads us to propose&fine grainarchitecture as a reasonable solution. Rigorous performance estimate is also provided for it. The single lowermost‐level processing element “ad hoc” designed by us, has been yet implemented in VLSI technology and is under test; it is suitable to work in very high granularity systems of bit‐sequential type (as “connectionist” architectures). Interconnection and data allocation policies, as well as possible process decomposition are also discussed.Results of the present investigation are the basis of a joint research program we have started with the Italian Space Agency (ASI) at the CGS Laboratory (Spatial Geodesy Center) in Mat

ISSN:1124-318X    

DOI:10.1002/ett.4460020607

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1991

数据来源: WILEY

摘要:

AbstractA vector computer implementation of a wide‐angle Synthetic Aperture Radar processor is presented. The choice of this architecture is convenient inasmuch Fast Fourier Transform codes and matrix multiplications can be efficiently implemented. Experiments and performance data of the processor are presente

ISSN:1124-318X    

DOI:10.1002/ett.4460020608

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1991

数据来源: WILEY

摘要:

AbstractThe Institute for Radio Frequency Technology of the German Aerospace Research Establishment (DLR) in Oberpfaffenhofen operates an experimental synthetic aperture radar, E‐SAR. The Radar configuration was developed by DLR [1, 2] and consists of a L/C/X‐band SAR System and antennas with a wide beamwidth in azimuth and elevation. The system is installed in a small Dornier DO 228 aircraft, which operates at low altitudes between 1000 m ‐ 3000 m above ground. Due to atmospheric turbulences, the aircraft is displaced from its nominal flight path, causing a variation of the phase history of the returned radar signal. This eventually results in a degraded image quality and therefore a highly accurate motion compensation becomes necessary. It is intended to integrate an inertial measurement unit (IMU) within the E‐SAR system to support the used motion compensation algorithm during data processing [3]. The required relative accuracy of the IMU can be determined by means of statistics i.e. an approach is demonstrated to estimate the power spectral density (PSD) of the tolerable uncompensated aircraft motion. The performance of an IMU motion compensation system has been evaluated by analysis, as well as by computer sim

ISSN:1124-318X    

DOI:10.1002/ett.4460020609

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1991

数据来源: WILEY

摘要:

AbstractThe aim of this paper is to show that some of the open problems in Synthetic Aperture Radar signal processing can be seen in a new and advantageous perspective if the received signals are represented in the time‐frequency domain. The joint time‐frequency representation makes easier the extraction of the information necessary for the formation of the synthetic aperture, responsible for the high cross‐range resolution. The proposed approach is applied to the imaging of moving objects and to the focusing of extended scenes, in presence of instabilities of the radar platform such that the conventional estimation techniques become insufficient. In particular, the time‐frequency analysis allows the estimation of the useful signal parameters even in case of undersampling. This allows the use of relatively low Pulse Repetition Frequencies(PRF), avoiding then the shortcomings due to highPRFs, like the reduction of the sizes of the monitorable areas or the data rate i

ISSN:1124-318X    

DOI:10.1002/ett.4460020610

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1991

数据来源: WILEY

摘要:

AbstractA new technique for the simultaneous measurement of all the target scattering matrix elements, recently proposed for general application to polarimetric radars, is analyzed for specific application to a fully polarimetric SAR. With reference to a focused SAR, the new concept of homopolar and heteropolar generalized ambiguity functions is introduced to evaluate the performance of the proposed technique in the presence of distributed targets, comparing it with the performance of the conventional polarimetric measurement technique based on pulse‐to‐pulse polarization switching. The possibility of synthesizing the heteropolar ambiguity function by means of pulse‐to‐pulse coding in order to improve performance of the single‐hit measurement technique is also po

ISSN:1124-318X    

DOI:10.1002/ett.4460020611

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1991

数据来源: WILEY